Differential roll crusher



March 5, 1940. s HARTSHQRN 2,192,310

DIFFERENTIAL' ROLL CRUSHER Filed June 30, 1938 5 Sheets-Sheet 1 INVENTOR March 5, 1940. 5, HARTSHQRN 2,192,310

DIFFERENTIAL R LL CRUSHER Filed June 30, 1938 3 Sheets-Sheet 2 INVENTOR 51 Qgaflllgfl Hark/101% QM ATTORN s March 5, 1940. 5 HARTSHORN 2,192,310

DIFFERENTIAL -ROLL CRUSHER Filed June 30, 1938 3 SheetsSheet 3 I FIIIIIIIIFI ITFWI'J willlllllll INVENTQR ATTORNEYS Patented Mar. r v I y g j 2,192,310 g DIFFERENTIAL ROLL CRUSHER t -Staifley D. number-n, Wayne, Pa. V g I Application June 30," 1938. Serial No; 216.686

7 v H eciaimefiwl. 83--45).' v g n 'Ihisinvention .relates'to improvements in because of such angle and velocity,, while the grinding mills oi the roller type in which'fma- -tendency of the screen to blind will be greatly terial is crushed against a grinding suriace"by reduced due to the decreased tendency of pary freely rotatable rollers which travel along {the ticles approximating the mesh size to become surface, comminuting the material 'byfdirect lodged in the meshes. For this purposethe 5 pressure and'rotated by their engagement with screen is arran'ged'around the discharge zone in 1 the material. Such mills 'are frequently fcbn such manner that'tl'iere is rapid rotary movestructed with a plurality of rollers traveling ment between the discharge and the screen, along an annular grinding surface whichmay be which may be accomplished either by rotating U either horizontal or vertical. M f

the screen relative to a stationary grinding sure-t 10 r g A feature of 'the inventionls the improvement" {face-by rotating. the grinding surfacerelative to; 1 0f h cmmimltmg 0 9 0 1' hefroiiers'f y v: the stationary screen, or, by combining these ducins I? idifletenti lfforgslidin "nievmhvbefeaturesi i" 1 a w t- I tween the crushing surfaceor'a rollerja'nd the- 1 Other'objects andiadvantages'willappearirom t 15 contiguous portion of the grinding suri'ac ""the tollowingdescription considered in connec- 15 is preferably accomplisnedhyretarding? fliraib tion with the accompanying drawings; in which; 1r; 8 on 01 each rqllerff andf'a specific Fig. 1 is aivertical central section; .through a" feature ofthe invention' is'theutilization-iorthis I ol1er-mlllprovided:;with ;a;rotatin& bowl; purpote Of a magneticflhrak iereb'y abiding Flg.i'2"isla horizontal section on line 1-1-2 0 so friction,eliminatingmaterial; f Fistlwithwairtsbrdkenaway; 1;. rotation at Io speedQandperniItting co" eni'ent K Fig.:s3z-isaa:*diagram (of. the: magnetic brakes, r t .t e f miimecti" "i" V l eed heaterrand;connections;a WP? brake m ey;,pe--empi qye;ana th" 4Jiis-caview similar to'.Fig.;14-showing, generated by the braking action may-be r'ollermill 1' of- "the air discharge .etyp r with: a; st -Ior instane,"1t drythe'material fed--througfia v ionary'grindingtsuriace; 9: U I'IRQDHB GWQ WB W o Flgi' b isiauiragmentarysidemelevationg ot a *rolleri'i housingk showing. a mechanical brake :in

" {centr'aiisection-;.1and 111:; w; 2'

Fig. 6 is a plan view ofutheamechanical brake structure." v T Inetheia construction shown-rill annulari ring LI 1'; which, preierablyt has an inner face I 8 sloping upwardly and outwardly 18cm rolling relation to ring I'I, each roller nxedmmarshaitxni-ieurnale 1 in;a; haf;t; cas H 23 pivotedeatr-zl toithevtep moyementrrtoward and trom- Vidd w'lth :s arm {2' I?? subst manye than tne' desi fi' screen""fd pfodlict a d; projecting matefla agaiiist the scree'ii it a iilbstantial s v gle and with sumeient ielocity' so tliat piirticles per end o the'sliattsaboirezealliit I3 larger than the screen opening will be rejected may beioi:themlnetleetmcin m eaeti sii'attzu istpronided. 1p

fixed to the upper end of shaft122 and stator elements 3| mounted in a suitable frame 32 on the'upper end of casing 23. The units 3| are suitably connected by leads 33 to an electric heating unit 34 surrounding the feed inlet passage 35 discharging through the top 25 of the housing into bowl It.

An annular screen 36 mounted beneath top 25 and having a lower margin immediately adjacent the upper edge of bowl i8 is arranged to receive material discharged centrifugally across the upper edge of ring surface |8 during operation.

A suitable fan arrangement may be provided for assisting the removal of the screenedprodnot, and in the form illustrated includes fan vanes 31 mounted on the outer face of bowl I6 between the bowl and the housing l5, and preferably having a suitable helical inclination to provide a substantial downward current of air. The blades l9 below the bowl will cooperate in discharging air from the bowl especially when employed in conjunction with a tangentially arranged outlet 20 as illustrated.

In the arrangement shown in Fig. 4 the basic mode of operation is similar but the bowl is stationary while the rollers are rotated as a unit. In this construction the bowl 40 is mounted through lugs 4| on the housing 42, and the shaft casings 23 are pivoted at 43 on forks 44 carried by head 45 fixed to shaft 46 driven through bevel gears 41 by drive shaft 48. The usual ploughs 45a mounted on a downward extension of head 45 are employed to raise the.

material from the bottom of bowl 40 into the path of rollers 2|.

The mill is of a well-known air discharge type, and the showing is therefore somewhat diagrammatic, as the inventive feature may be incorporated in known mills of this type having various features and details omitted in the present disclosure. In the illustrated arrangement the air enters through passage 23, travels through the grinding zone to pick up the pulverulent material in any desired manner, as by passing around the periphery of bowl 40, and thence upwardly and out of casing 42 through outlet 42a.- The air is propelled in any desired manner, as by the usual fan (not shown).

In this arrangement the magnetic brake units 3| are mounted in housings 48 on the shaft casings 23 and are connected through flexible leads 53 with slip rings 5| on shaft 43, the rings being connected through brushes 53 with the leads 33 connected to the heating coil 34. Brushes 53 may? carried by bracket 52 mounted on hous- The-feed passage 55 carrying heater 34 extends through the side of casing 42 in position to discharge the feed into bowl 43. .In this arrangement the screen 35 has not been shown, but such omission is not restrictive, since the principles of screen arrangement and operation set forth hiil'lein are obviously applicable to this type of m While brakes of the magnetic type have certain advantages, the rotation of the roller shafts may be retarded in other ways.

A mechanical brake of-the centrifugal type suitable. for this purpose is illustrated in Figs. 5 and 6. It includes a frame disc 53 fixed toshaft 22 and suitable supporting radial arms 53 biased toward the center by spring 33 extending around pins II on arms .33. Said arms are radially slidable in guideways ilattheouteredgeofdisclland carry shoes 63 engageable with the inner face of brake drum 54 mounted on the upper end of shaft casing 23.

The differential movement between the rollers and the grinding surface may also be produced by driving each roller at a rate of rotation greater than that resulting from rolling contact with the material. This may be conveniently accomplished by an electric motor connected to the roller shaft. Since the magnetic brakes heretofore described are of the motor-generator type, they can be employed as motors, it being of course understood that they are suitably wound and connected in well known manner for this purpose. Moreover, the same unit may be used alternatively as a motor or as a magnetic brake, as by connecting leads 33 to a source of power G.

The electrical arrangement is of course diagrammatic and omits features and characteristics known to electrical engineers as necessary or desirable but which are unnnecessary to an understanding of this invention. However, since the electrical characteristics of the heating unit 34 when the units 3| are employed as brakes should be substantially different from their characteristics when said units are driven as motors, a separate heating unit 34a is disclosed. Switch 55 is suitably connected to units 34, 34a, generator G and magnetic units 4| as shown in Figure 3 so that when units 3| are operated as magnetic brakes, the generater current will pass through heating unit 34, and when they are connected to generator G and operate as motors the current from the generator will pass through heating unit 34a.

The method of operation will be in general apparent to those familiar with mills of the illustrated type. In the arrangement shown in Fig. 1 the material discharged through passage 35 into bowl I6 is ground against bowl ring IT by rollers 2|, being forced upwardly along face |8 of the ring by centrifugal force and being discharged in a substantially tangential direction by centrifugal force into contact with screen 36. The over-size will fall back into bowl It for regrinding while the fines, assisted by the fan vanes 31 and blades l3 will pass downwardly between bowl l5 and the housing l5 and out through passage 20. when bowl I6 is rotated at full speed rollers 2| will tend to rotate at the same peripheral speed as face l8 but will be retarded by the action of the magnetic brake units 3| on, rotor 30, which will produce substantial slippage between rollers 2| and grinding face Hi. This action will subject the material between the rollers and said .face to a-sliding grinding action in addition to a substantial speed, thereby avoiding any increase in the starting torque of motor I.

While the invention has been illustrated in its application to a roller mill of the type employing a plurality-of rollers traveling along a horizontal ring, it will be apparent that the invention is not restricted to this construction and that various modifications may be made within the scope of the invention as set forth in the claims. Moreover while an annular screen registering with the margin of abowl and arranged for relative rotation between the screen and the bowl has been illustrated, the -invention as it relates to such screen is not restricted in its broadest aspects to this construction or arrangement.

I claim:

aioaaio 1. A roller mill comprising an annular grinding surface, freely rotatable grinding rollers traveling along the grinding surface in position for rotation by grinding engagement with material on said surface, shafts on which the rollers are fixed, generator type magnetic brakes associated with said shafts for retarding the rotation of the rollers and shafts, and means for heating material fed to the mill including an electrical heater energized by current from-the generator type brakes.

2. A roller mill comprising a grinding bowl, a frame carrying rotatable grinding rollers within the bowl in position to be rotated by contact with material carried on the inner surface of the bowl, means for producing relative rotation between said frame and said bowl, shafts journaled in said frame carrying said rollers, a plurality of rotor drives one for each of said shafts, a plurality of driving members carried by said frame one for each rotor drive, and means for applying a variable torque between each driving member and its corresponding rotor so as to impose a variable torque on said shafts and rollers and independently vary the relative grinding speed of each roller with respect to the surface of the bowl and with respect to the speeds of the remaining rollers.

3. A roller mill as set forth in claim 2 in which each rotor drive and its cooperating driving member compose a motor generator unit adapted to apply torque in either direction on the corresponding roller shaft.

4. A roller mill comprising a grinding bowl, a frame carrying grinding rollers within the bowl, means for producing relative rotation between said frame and said bowl, said rollers being rotated on their axes" by grinding engagement with material carried on the inner surface of the bowl and means'for superimposing on each of said rollers separately a variable braking torque dependent upon the speed of rotation of each respective roller and producing an independently variable sliding movement of the operative grinding face of each roller relative to the grinding bowl.

5. A roller mill as set mm in claim 4 m which the grinding bowl is rotated and the roller carrying frame is substantially angularly immovable in operation.

6. A roller mill as set forth in claim4 in which generator type magnetic brakes are associated with the roller shafts to apply the variable braking torque on each roller.

STANLEY D. HARTSHORN. 

